In a fifth-generation mobile communication system (referred to as 5G), such a technical demand is proposed as a rate of gigabits per second (Gbps) for user experience, an ultrahigh flow density, an extra-large number of connections, an improved spectral efficiency, a reduced time delay, or the like.
In order to meet a requirement of 5G for the extra-large number of connections, a non-orthogonal multiple access technology is introduced.
As for a requirement to support a mobile Internet of Things (IoT) application scenario of 5G with a large number of connections, a low time delay and high reliability, when an uplink scheduling algorithm of a 4G system is still used, it needs a significant amount of control signaling, with relatively high signaling overhead. In the case that the number of connections reaches to a certain value, the number of scheduled users is limited by control channel resources. Therefore, as for the mobile IoT application, a scheduling-free mechanism should be utilized.
In a long term evolution (LTE) system, since a scheduling mechanism is adopted, a base station knows a transmission time and a position of an uplink pilot for each user, and accordingly performs uplink detection. However, in the case that a terminal employs a scheduling-free access mechanism, the base station does not know when the terminal transmits data. In this case, how a base station side performs the uplink detection is a problem to be solved currently.